engleski

INFLUENCE OF DEEP CRYOGENIC TREATMENT ON MICROSTRUCTURE OF ADI

Application of deep cryogenic treatment in heat treatment processes of different types of steel showed significant influence on their mechanical and tribological properties. A lot of research on that field has been performed also on other kinds of material such as hard metal, grey cast iron, aluminum and aluminum alloys, etc. In this research influence of deep cryogenic treatment on properties of austempered ductile iron has been investigated. Base material for research was perlitic – ferritic ductile cast iron grade EN-GJS-600 (DIN GGG 60) which was austempered and deep cryogenically treated and afterward tempered on different temperatures. Hardness of specimens was measured by use of Vickers hardness method, and abrasion wear resistance of specimens was tested with standard ASTM “dry sand/rubber wheel” method. Preliminary results showed that deep cryogenic treatment did not affect significantly on hardness of tested samples, but it increases the abrasion wear resistance. Microstructures of all samples were characterized in order to define the microstructural changes during deep cryogenic treatment that influenced on mechanical and tribological properties of ADI. Therefore, metallographic specimens were etched with several etchants (Beraha-Martensite, SMB – sodium metabisulfite, KLEMM I and Picral) and analyzed by use of light microscopy and scanning electron microscopy. The microhardness of different phases in revealed microstructures was also measured. Obtained results show that deep cryogenic treatment in combination with the different tempering temperatures affects the matrix microstructure of ductile cast iron and ADI, which has led to increased resistance to abrasive wear of the surveyed states.

deep cryogenic treatment; ADI; nodular cast iron; microstructure; FE SEM

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